Apparatus for plating cylinder

ABSTRACT

Provided is a plating apparatus for a cylinder, which is capable of extending service life of the entire apparatus in a technology of plating a cylinder, eliminating hardness nonuniformity of a plating layer on a cylinder surface by achieving a uniform hardness, and suppressing oxidation of a tip of chuck means. The plating apparatus for a cylinder includes: a plating bath to be filled with a plating solution; chuck means for holding a long cylinder at both ends in a longitudinal direction so as to be rotated and energized, and accommodating the long cylinder in the plating bath; and a pair of opposed insoluble electrodes which is vertically installed so as to face both side surfaces of the long cylinder in the plating bath, and is supplied with a predetermined current. The chuck means includes thermal cooling means, and the thermal cooling means includes a cooling medium and causes the cooling medium to circulate to cool a cylinder holding section of the chuck means so that heat accumulation in the long cylinder, in particular, a cylinder end portion and the cylinder holding section of the chuck means is eliminated.

TECHNICAL FIELD

The present invention relates to a plating apparatus for a cylinder, which is configured to perform plating using an insoluble electrode as a plating material for forming a printing surface, for example, copper plating or chromium plating, on an outer peripheral surface of a long cylinder, for example, a hollow cylindrical gravure cylinder (also called a plate-making roll) used for gravure printing. In particular, the present invention relates to a plating apparatus for a cylinder, in which thermal cooling means is provided in chuck means for holding the cylinder to cool the cylinder, in particular, cylinder end portions and cylinder holding sections of the chuck means during plating treatment, thereby eliminating heat accumulation in the cylinder, in particular, in the cylinder end portions and the cylinder holding sections of the chuck means, and keeping uniform plating with respect to the outer peripheral surface of the cylinder.

BACKGROUND ART

In gravure printing, minute concave portions (cells) are formed on a gravure cylinder in accordance with plate-making information to produce a printing surface, and the cells are filled with ink so that the ink is transferred to an object to be printed. In a general gravure cylinder, a cylindrical iron core or aluminum core (hollow roll) is used as a base, a plurality of layers such as an underlying layer and a separation layer are formed on an outer peripheral surface of the base, and a copper plating layer (plating material) for forming a printing surface is formed on the plurality of layers. Then, cells are formed on the copper plating layer in accordance with plate-making information by a laser exposure apparatus, and thereafter, the resultant base is plated with chromium or the like for enhancing printing durability of a gravure cylinder. In this manner, plate making (production of a printing surface) is completed.

Conventionally, as a method and apparatus for performing copper plating on an outer peripheral surface of a gravure cylinder, the use of a phosphorus-containing copper ball as a soluble anode is well known. According to the conventional method and apparatus, both ends in a longitudinal direction of a gravure cylinder are held so as to be rotated and energized by a pair of roll chucks, the gravure cylinder is accommodated in a plating bath in which a plating solution is stored while the gravure cylinder is being rotated, and a current with a current density of about 10 to 15 A/dm² is allowed to flow between the phosphorus-containing copper ball (soluble anode) in the plating solution and the gravure cylinder (cathode), to thereby deposit copper on an outer peripheral surface of the gravure cylinder, which functions as a cathode, with the result that copper plating is performed (for example, see Patent Documents 1 and 2).

However, in general, a phosphorus-containing copper ball used in a copper plating method and apparatus for a gravure cylinder contains 350 to 700 ppm of phosphorus and 2 to 5 ppm of oxygen, and the rest of the ball contains copper and impurities. Due to the impurities contained in the ball inevitably, anode sludge is generated during plating treatment, which causes defects such as rashes (minute protrusions) and pits (pinholes) on the outer peripheral surface of the gravure cylinder. Although there is a phosphorus-containing copper ball of high purity for producing a semiconductor and the like, such a ball is expensive and is not adopted for a gravure cylinder in terms of cost-efficiency. Further, in order to prevent the dissolution amount of a phosphorus-containing copper ball in a copper plating solution from increasing excessively to enhance the copper ion concentration, making it impossible to perform appropriate plating treatment, it is also necessary to dilute the solution by removing a plating solution periodically, thereby adjusting the copper ion concentration appropriately and disposing of a waste liquid. Further, a current is concentrated in the vicinity of both ends of the gravure cylinder, and hence the peripheral surface in the vicinity of both ends is plated thicker than a body portion, with the result that it is necessary to separately perform treatment for obtaining a uniform thickness of plating by follow-up polishing or the like.

On the other hand, in addition to a method using a phosphorus-containing copper ball as a soluble anode, a copper plating method using an insoluble anode is known. As a copper plating method and apparatus for a gravure cylinder using an insoluble anode, for example, a titanium plate coated on the surface with iridium oxide or the like is used as an insoluble anode, a plating bath and a copper dissolution bath are prepared, the copper plating material (e.g., copper oxide or copper carbonate) is dissolved in the dissolution bath, the resultant solution is supplied to a plating solution in the plating bath, and a current is supplied between an insoluble anode and a gravure cylinder forming a cathode. In this manner, copper plating is performed (for example, see Patent Document 3).

According to the above-mentioned method and apparatus, anode sludge is not generated so that defects such as rashes and pits are not caused, but there is still a problem that the peripheral surface in the vicinity of both ends of a gravure cylinder is plated thick. In order to solve this problem, the applicant of the present application has already proposed a copper plating method and apparatus for a gravure cylinder in which an insoluble anode positioned below a gravure cylinder is configured so as to be lifted in a plating bath, and the insoluble anode is brought close to a lower surface of the gravure cylinder with a gap of 5 mm to 30 mm in accordance with gravure cylinders of various sizes, with the result that a current is not concentrated in the vicinity of both ends of the gravure cylinder, plating with a uniform thickness can be performed over the full length of the gravure cylinder, and the concentration of copper and the concentration of sulfuric acid in the plating solution can be adjusted automatically (see Patent Document 4).

Still further, in the above-mentioned proposal, there are the following problems. That is, an insoluble anode is placed directly in the plating solution, and hence the consumption amount of additives such as a brightener and a burn prevention agent is remarkably large. A current density is about 15 to 20 A/dm² and a voltage is about 10 to 15 V for the purpose of preventing a burn, and hence plating treatment takes a long time, which results in a large power supply cost. The uniformity of a plating thickness is insufficient. The insoluble anode is positioned below the gravure cylinder, and hence visibility and operability are poor. Considering these problems, the applicant of the present application has already proposed a copper plating method and apparatus for a gravure cylinder, in which a hollow cylindrical gravure cylinder is held at both ends in a longitudinal direction and accommodated in a plating bath filled with a copper plating solution, the gravure cylinder is rotated at a predetermined speed and supplied with a current so as to become a cathode, and a pair of anode chambers in the shape of a long box that is vertically installed slidably so as to face both sides of the gravure cylinder in the plating bath and contains insoluble anodes supplied with a current so as to become an anode are brought close to both side surfaces of the gravure cylinder with a predetermined interval to perform copper plating on an outer peripheral surface of the gravure cylinder (Patent Document 5).

According to the above-mentioned proposal, a copper plating method and apparatus for a gravure cylinder that provide good visibility and operability can be provided, in which copper plating with a uniform thickness compared to the conventional example can be performed over the full length of a gravure cylinder without generating defects such as rashes and pits irrespective of the size of the gravure cylinder, the concentration of a copper plating solution can be managed automatically, the consumption amount of additives can be reduced, plating treatment can be performed in a short period of time, and a power supply cost can be reduced. However, from the viewpoint of the uniformity of a thickness of copper plating over the full length of a gravure cylinder 300, the uniformity is not necessarily sufficient, and the following phenomenon has not been solved sufficiently. That is, in the vicinity of both ends of the gravure cylinder 300 (particularly, portions of about 50 mm to 200 mm from the both ends), a current is concentrated, and hence, a peripheral surface in the vicinity of each end is plated thicker than a body portion, with a result that a thick plating layer of about 150 μm is formed.

The applicant of the present application has further continued to study extensively, and obtained a new landmark finding that, by dividing an insoluble electrode and adjusting a potential of each divided electrode, the current concentration in cylinder end portions can be prevented effectively. Thus, the applicant of the present application has provided a plating method and apparatus for a cylinder that provide good visibility and operability, in which copper plating with a more uniform thickness can be performed over the full length of a cylinder without generating defects such as rashes and pits irrespective of the size of the cylinder, the concentration of a copper plating solution can be managed automatically, the consumption amount of additives can be reduced, plating treatment can be performed in a short period of time, and a power supply cost can be reduced. The applicant of the present application has also proposed a plating method and apparatus for a cylinder capable of greatly preventing the vicinity of both ends of the cylinder from being plated thicker than the body portion, to thereby eliminate or simplify treatment for obtaining the uniform thickness of plating, such as follow-up polishing (Patent Document 6).

The above-mentioned plating method for a cylinder is a plating method for a cylinder in which a long cylinder is held at both ends in a longitudinal direction and accommodated in a plating bath filled with a plating solution, the cylinder is rotated at a predetermined speed and supplied with a current so as to become a cathode, and a pair of electrode chambers in the shape of a long box that is vertically installed slidably so as to face both sides of the cylinder in the plating bath and contains insoluble electrodes supplied with a predetermined current are brought close to both side surfaces of the cylinder with a predetermined interval to perform plating on an outer peripheral surface of the cylinder. In this method, the insoluble electrode is divided into a large number of divided electrodes, and the insoluble electrode portions at least corresponding to the vicinity of both ends in a longitudinal direction of the cylinder are respectively divided into at least three divided electrode groups. Each divided electrode group has one or more divided electrodes, and a potential of the divided electrode group is controlled so as to adjust a thickness of a plating layer on the outer peripheral surface of each end of the cylinder (Patent Document 6, claim 1).

Further, the above-mentioned plating apparatus for a cylinder includes a plating bath to be filled with a plating solution, chuck means for holding a long cylinder at both ends in a longitudinal direction so as to be rotated and energized, and accommodating the cylinder in the plating bath, and a pair of electrode chambers in the shape of a long box that is vertically installed slidably so as to face both sides of the cylinder in the plating bath and contains insoluble electrodes supplied with a predetermined current, the electrode chamber being brought close to both side surfaces of the cylinder with a predetermined interval to perform plating on an outer peripheral surface of the cylinder. The insoluble electrode is divided into a large number of divided electrodes, and the insoluble electrode portions at least corresponding to the vicinity of both ends in a longitudinal direction of the cylinder are respectively divided into at least three divided electrode groups. Each divided electrode group has one or more divided electrodes, and a potential of the divided electrode group is controlled so as to adjust a thickness of a plating layer on the outer peripheral surface of each end of the cylinder (Patent Document 6, claim 1).

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP Sho 57-36995 B -   Patent Document 2: JP Hei 11-61488 A -   Patent Document 3: JP 2005-29876 A -   Patent Document 4: JP 2005-133139 A -   Patent Document 5: WO 2006-126518 -   Patent Document 6: JP 2007-224321 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the plating method and apparatus for a cylinder of the above-mentioned proposal, it is understood that the vicinity of both ends of a cylinder can be greatly prevented from being plated thicker than a body portion to eliminate or simplify treatment for obtaining the uniform thickness of plating, such as follow-up polishing. However, from the viewpoint of obtaining the uniform thickness of a plating layer, such plating method and apparatus cannot be considered to be perfect. The applicant of the present application has continuously researched for a technology capable of forming a plating layer uniform in thickness in a technology of plating a cylinder, and obtained a finding that heat is accumulated in a cylinder during plating treatment to reach high temperature, and holding side ends of chuck means for holding the cylinder at high temperature also reach high temperature, with the result that a holding function thereof is degraded, the uniformity of rotation of the cylinder is degraded, and the uniformity of a thickness of the plating layer is degraded. Further, when the temperature of the cylinder rises, the hardness of the plating layer obtained by plating including copper plating and chromium plating is lowered to decrease the hardness of the plating layer, particularly, on both end surfaces of the cylinder. Particularly when the temperature of a tip of the chuck means rises, the tip of the chuck means is oxidized to be covered with an oxide coating film to cause conduction defects. When the temperature of the tip of the chuck means rises, the tip of the chuck means is oxidized and coated with an oxide coating film so that a flow of a current becomes poor. At this situation if an attempt is made so as to allow a current to flow more, then the temperature of the tip of the chuck means rises to advance the oxidation with a result that the formation of the oxide coating film increases. Such a bad cycle is problematically caused.

In order to solve the above-mentioned problems inherent in the related art, the applicant of the present application has further conducted studies, and consequently, found that thermal cooling means is provided in the chuck means for holding the cylinder to cool the cylinder, in particular, cylinder end portions and cylinder holding sections of the chuck means during plating treatment, to thereby eliminate heat accumulation in the cylinder, in particular, the cylinder end portions and the cylinder holding sections of the chuck means, keep uniform heat accumulation in the cylinder during plating treatment, and suppress oxidation of the tip of the chuck means. Accordingly, the applicant of the present application has achieved the present invention.

It is an object of the present invention to provide a plating apparatus for a cylinder, which is capable of extending service life of the entire apparatus in a technology of plating a cylinder, eliminating hardness nonuniformity of a plating layer on a cylinder surface by achieving a uniform hardness, suppressing oxidation of the tip of chuck means, suppressing the above-mentioned bad cycle that an oxide coating film is formed at the tip of the chuck means, and performing plating with a uniform thickness over the full length of the cylinder without causing defects such as rashes and pits irrespective of the size of the cylinder.

Means for Solving Problems

According to the present invention, there is provided a plating apparatus for a cylinder, including: a plating bath to be filled with a plating solution; chuck means for holding a long cylinder at both ends in a longitudinal direction so as to be rotated and energized, and accommodating the cylinder in the plating bath; and a pair of opposed insoluble electrodes which is vertically installed so as to face both side surfaces of the cylinder in the plating bath, and is supplied with a predetermined current, the pair of opposed insoluble electrodes being brought close to both the side surfaces of the cylinder with a predetermined interval to perform plating on an outer peripheral surface of the cylinder.

The chuck means includes thermal cooling means, and the thermal cooling means includes a cooling medium and causes the cooling medium to circulate to cool a cylinder holding section of the chuck means so that heat accumulation in the cylinder, in particular, a cylinder end portion and the cylinder holding section of the chuck means is eliminated.

It is preferred that the thermal cooling means include: a main pipe portion provided adjacent to the cylinder holding section of the chuck means; a cooling medium flow path formed in the main pipe portion, for distributing a cooling medium; an external flow path provided in communication with an inflow port and an outflow port of the cooling medium flow path; a cooling medium sealed in the cooling medium flow path and the external flow path; circulation pump means which is installed in the external flow path and functions so that the cooling medium sealed in the cooling medium flow path and the external flow path flows into the cooling medium flow path from the external flow path through the inflow port and flows out to the external flow path from the cooling medium flow path through the outflow port; and a cooling device which is installed in the external flow path and functions to cool the cooling medium flowing out of the outflow port.

In the plating apparatus for a cylinder of the present invention, it is preferred that the insoluble electrode have a shape in which a lower part is curved inward, that the insoluble electrode be configured so as to rotate about an upper end of the insoluble electrode, and that a thickness of a plating layer on the outer peripheral surface of the cylinder be adjusted by controlling an interval of closeness to the cylinder.

In the plating apparatus for a cylinder of the present invention, regarding the curved shape of the lower part of the insoluble electrode, the effect is enhanced as long as the lower part is curved inward. However, it is preferred that the lower part have a curved shape so as to conform to the curved outer peripheral surface of the cylinder.

The interval at which the insoluble electrode is brought close to the cylinder side surface is about 1 mm to 50 mm, preferably about 3 mm to 40 mm, most preferably about 5 mm to 30 mm. From the viewpoint of the uniformity of a plating thickness, it is preferred that the insoluble electrode be brought as close to the cylinder side surface as possible. However, when the insoluble electrode is brought too close to the cylinder side surface, the insoluble electrode and the cylinder may come into contact with each other during plating treatment.

A copper plating solution can be used as the plating solution, and a gravure cylinder can be used as the cylinder. Further, it is preferred that the copper plating solution contain copper sulfate, sulfuric acid, chlorine, and an additive. When a gravity of the copper plating solution and a concentration of sulfuric acid are measured, in the case where the gravity is too high, it is preferred to supply water, and in the case where the concentration of sulfuric acid is too high, it is preferred to supply cupric oxide powder. Thus, it is not necessary to perform the conventional periodic maintenance of the copper plating solution and the disposal of a waste liquid. Note that, it is preferred that impurities be removed from the copper plating solution through a filter. Further, a chromium plating solution can also be used as the plating solution so as to perform chromium plating.

Effects of the Invention

According to the present invention, the thermal cooling means is provided in the chuck means for holding the cylinder to cool the cylinder, in particular, the cylinder end portions and the cylinder holding sections of the chuck means during plating treatment, to thereby eliminate the heat accumulation in the cylinder, in particular, the cylinder end portions and the cylinder holding sections of the chuck means, extend the service life of the entire apparatus in the technology of plating a cylinder, eliminate the hardness nonuniformity of a plating layer on a cylinder surface by achieving a uniform hardness, suppress the oxidation of the tip of the chuck means, and suppress the above-mentioned bad cycle that an oxide coating film is formed at the tip of the chuck means. In particular, the present invention exhibits such a remarkable effect that the plating apparatus is suitably used for plating treatment of a gravure cylinder.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic explanatory front view illustrating an example of a configuration in which thermal cooling means is provided in chuck means of a cylinder in a plating apparatus for a cylinder of the present invention.

FIG. 2 is a schematic enlarged explanatory perspective view illustrating an example of a mode of placing an insoluble electrode in the plating apparatus for a cylinder of the present invention.

FIG. 3 is a schematic explanatory side view illustrating an example of a basic configuration of the plating apparatus for a cylinder of the present invention.

FIG. 4 is an explanatory plan view illustrating an example of a slide mechanism for the insoluble electrode in the present invention.

FIG. 5 is an explanatory side view illustrating an example of the slide mechanism for the insoluble electrode in the present invention.

FIG. 6 is an explanatory front view illustrating an example of the slide mechanism for the insoluble electrode in the present invention.

FIG. 7 is an explanatory front view illustrating an operation example of the insoluble electrode in the present invention.

FIG. 8 is a schematic explanatory front view illustrating an example of placing the insoluble electrode in the plating apparatus for a cylinder of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention is described with reference to the attached drawings. Illustrated examples are shown for illustrative purposes. Therefore, it is natural that they can be modified variously as long as they do not extend beyond the technical idea of the present invention.

FIG. 3 is a schematic explanatory side view illustrating an example of a basic configuration of the plating apparatus for a cylinder of the present invention. In FIG. 3, reference symbol 2 denotes a plating apparatus for a cylinder of the present invention, and as a specific illustrated example, a copper plating apparatus for a gravure cylinder is described.

The copper plating apparatus 2 for a gravure cylinder of the present invention performs copper plating on the outer peripheral surface of a gravure cylinder 300 in a long hollow cylindrical shape, and includes a plating bath 10, a pair of chuck means 14, 14 for supporting the gravure cylinder 300, and a pair of insoluble electrodes 22, 22 that are vertically installed in the plating bath 10 through use of busbars 20, 20. The plating bath 10 has a regular configuration substantially similar to those of conventional apparatuses (see Patent Documents 1 to 3, 5, and 6), and hence the repeated descriptions thereof are omitted. The plating bath 10 is used for plating treatment, which is filled with a copper plating solution 304 and is capable of soaking the gravure cylinder 300 in the copper plating solution 304 completely. On the periphery of the plating bath 10, a collecting port 12 for collecting the overflowed copper plating solution 304 (see FIGS. 3 to 5) is provided, and below the plating bath 10, a reservoir bath 70 for storing the copper plating solution 304 is provided in communication with the collecting port 12 (see FIG. 3). In the reservoir bath 70, a heater 86 and a heat exchanger 88 for keeping the copper plating solution 304 at a predetermined liquid temperature (e.g., about 40° C.) are provided, and a filter 80 for removing impurities in the copper plating solution 304, a pump P1 for pumping up the copper plating solution 304 from the reservoir bath 70 so that the copper plating liquid 304 circulates to the plating bath 10, and the like are provided (see FIG. 3).

The chuck means 14, 14 are a roll chuck apparatus for holding the gravure cylinder 300 at both ends in a longitudinal direction and accommodating the gravure cylinder 300 in the plating bath 10, and includes a spindle 16 axially supported by a bearing 6. The chuck means 14, 14 are driven to rotate at a predetermined speed (e.g., about 120 rpm) through an intermediation of a chain C and a sprocket 18 by a cylinder rotation motor 306 provided on a base 4, and can be energized so that the gravure cylinder 300 becomes a cathode (see FIG. 3). In addition, a cover plate 8 that can be opened and closed above the plating bath 10, a discharge duct 11, and the like are provided appropriately (see FIG. 3).

The feature of the present invention resides in that thermal cooling means is provided in chuck means for holding the cylinder to cool the cylinder, in particular, cylinder end portions and cylinder holding sections of the chuck means during plating treatment, to thereby eliminate heat accumulation in the cylinder, in particular, in the cylinder end portions and the cylinder holding sections of the chuck means, keep uniform heat accumulation in the cylinder during the plating treatment, and obtain a further uniform thickness of a plating layer in plating of the cylinder. FIG. 1 is a schematic explanatory front view illustrating an example of a configuration in which thermal cooling means is provided in chuck means of the cylinder in the plating apparatus for a cylinder of the present invention. FIG. 3 is a schematic explanatory side view illustrating an example of a basic configuration of the plating apparatus for a cylinder of the present invention.

In FIGS. 1 and 3, the pair of chuck means 14 for holding the cylinder 300 at both ends thereof are respectively provided with thermal cooling means 100 (in FIG. 1, only one chuck means 14 is illustrated). The chuck means 14, 14 hold both ends of the cylinder 300 with cylinder holding sections (generally, called chuck cones) 14 a, 14 a.

The thermal cooling means 100 includes a main pipe portion 102 adjacent to the cylinder holding section 14 a of the chuck means 14. In the main pipe portion 102, a cooling medium flow path 106 for distributing a cooling medium 104 is formed. In a trailing end 14 b of the chuck means 14, an inflow port 108 and an outflow port 110 for an inflow and an outflow of the cooling medium 104 are formed in communication with the cooling medium flow path 106. Reference symbol 112 denotes an external flow path provided outside the main pipe portion 102 in communication with the inflow port 108 and the outflow port 110. As the cooling medium 104, a cooling medium having two phases of gas and liquid, for example, distilled water is used preferably. However, needless to say, other known cooling media can be used.

The cooling medium 104 is sealed in the cooling medium flow path 106 and the external flow path 112. Reference symbol 114 denotes circulation pump means, which is installed in the external flow path 112. The circulation pump means 114 functions so that the cooling medium 104 sealed in the cooling medium flow path 106 and the external flow path 112 flows into the cooling medium flow path 106 from the external flow path 112 through the inflow port 108, and the cooling medium 104 flows out to the external flow path 112 from the cooling medium flow path 106 through the outflow port 110. Reference symbol 116 denotes a cooling device, which is installed in the external flow path 112 and functions to cool the cooling medium 104 flowing out of the outflow port 110.

In the configuration of FIG. 3, when the cylinder 300 is plated by applying a required potential to the respective insoluble electrodes 22, 22, the cylinder 300 generates heat to reach a high temperature, and the cylinder holding sections 14 a, 14 a of the chuck means 14, 14 for holding the cylinder 300 at both ends also reach a high temperature. The increase in temperature of the cylinder holding sections 14 a, 14 a of the chuck means 14, 14 occurring during the plating treatment is eliminated by cooling the cylinder, in particular, the cylinder end portions and the cylinder holding sections of the chuck means, and hence the heat accumulation in the cylinder, in particular, the cylinder end portions and the cylinder holding sections of the chuck means is eliminated, which prevents an extreme increase in temperature of the cylinder 300 and also prevents an increase in temperature of the cylinder holding sections 14 a. Thus, the degradation in holding function of the chuck means 14 can also be prevented, and the thickness of a plating layer can be kept further uniform in plating treatment of the cylinder.

FIG. 8 is a schematic explanatory front view illustrating an example of placing the insoluble electrode in the plating apparatus for a cylinder of the present invention. FIG. 2 is a schematic enlarged explanatory perspective view illustrating main portions of the plating apparatus for a cylinder of the present invention. In the copper plating apparatus 2 for a gravure cylinder of the present invention, as illustrated in FIG. 8, the busbars 20, 20 are fixed to support bars 23, 23 through an intermediation of auxiliary members 21, and the insoluble electrodes 22, 22 are vertically installed to the busbars 20, so as to face respective sides of the gravure cylinder 300 held by the chuck means 14 in the plating bath 10. As the insoluble electrode 22, a titanium plate coated on the surface with iridium oxide or the like is used.

In the present invention, as illustrated in FIGS. 8 and 2, a configuration can also be adopted in which the insoluble electrodes 22, 22 have lower parts curved inward. Regarding the curved shape of the lower parts of the insoluble electrodes 22, 22, the effect is enhanced as long as the lower parts are curved inward. However, it is preferred that the lower parts have a curved shape so as to conform to the curved outer peripheral surface of the gravure cylinder 300. Further, the insoluble electrodes 22, 22 are configured so as to rotate about upper ends thereof, and the thickness of the plating layer on the outer peripheral surface of the gravure cylinder can be adjusted by controlling the interval of closeness to the gravure cylinder 300. As a mechanism for allowing the insoluble electrodes 22, 22 to rotate, any well-known rotation mechanism only needs to be adopted. However, for example, a mechanism as illustrated in FIG. 7 can be adopted. FIG. 7 is an explanatory front view illustrating an operation example of the insoluble electrode in the present invention. In FIG. 7, reference symbols 300A and 300B respectively denote a cylinder having a maximum diameter and a cylinder having a minimum diameter virtually. Reference symbol 64 denotes a rotation shaft fixed to the plating bath 10. The busbar 20 is fixed to the rotation shaft 64, and the insoluble electrode 22 is mounted to a tip of the busbar 20. Due to such a configuration, when the rotation shaft 64 is rotated, the busbar 20 rotates, and the insoluble electrode 22 also rotates. Accordingly, as illustrated in FIG. 7, the insoluble electrode 22 is rotated in accordance with the diameter of the cylinders 300, 300A, and 300B, and the distance of closeness of the lower end thereof to the surface of the cylinders 300, 300A, and 300B is controlled to an optimum position, to thereby perform plating.

Next, the mechanism that enables the pair of insoluble electrodes 22, 22 to be slide on both sides of the gravure cylinder 300 is not particularly limited. An example is described with reference to FIGS. 4 to 6. FIG. 4 is an explanatory plan view illustrating an example of a slide mechanism for the insoluble electrode in the present invention. FIG. 5 is an explanatory side view illustrating an example of the slide mechanism for the insoluble electrode in the present invention. FIG. 6 is an explanatory front view illustrating an example of the slide mechanism for the insoluble electrode in the present invention. As illustrated in FIGS. 4 to 6, the base 4 is provided upright outside the front surface of the plating bath 10, and linear rails 50, 52 are provided on an inner wall surface of the base 4. Racks 60, 62 are provided so as to reciprocate due to the forward and reverse rotations of spur gears 35, 38 in parallel to the linear rails 50, 52, and are connected to guide members 54, 55 slidably engaged with the linear rails 50, 52 through an intermediation of mounting frames 58, 59.

Regarding the spur gears 35, 38 that allow the racks 60, 62 to reciprocate, the spur gear 35 is fixed to the base 4 with a fixture 40 so as to rotate coaxially with a sprocket 45 on the outer wall surface side of the base 4. On the other hand, the spur gear 38 is fixed to the base 4 with a fixture 39 so as to rotate coaxially with a sprocket 48 on the outer wall surface side of the base 4. Right below the sprocket 45, a sprocket 44 is provided so as to rotate coaxially with a spur gear 34, and right below the other sprocket 48, a sprocket 47 is provided so as to rotate coaxially with a sprocket 46. On the outer wall surface of the base 4, a geared motor 30 is installed through an intermediation of a mounting angle bar 31, and a spur gear 32 is provided. A spur gear 33 is provided so as to rotate coaxially with a sprocket 43 and to be engaged with the spur gear 32. A chain C1 is engaged between the sprockets 43, 46, a chain C2 is engaged between the sprockets 44, 45, and a chain C3 is engaged between the sprockets 47, 48. Thus, due to the forward and reverse drive of the geared motor 30, the spur gears 35, 38 rotate forwardly and reversely, and the racks 60, 62 reciprocate. In synchronization therewith, the insoluble electrodes 22, 22 are slidable accurately along the linear rails 50, 52 (see FIGS. 4 and 5).

The interval at which each insoluble electrodes 22, 22 are brought close to the side surfaces of the gravure cylinder 300 is about 1 mm to 50 mm, preferably about 3 mm to 40 mm, most preferably about 5 mm to 30 mm. From the viewpoint of the uniformity of a plating thickness, it is considered to be preferred that the insoluble electrodes 22, 22 be brought as close to the side surfaces of the gravure cylinder 300 as possible. However, when the insoluble electrodes 22, 22 are brought too close to the side surfaces of the gravure cylinder 300, the insoluble electrodes 22, 22 and the gravure cylinder 300 may come into contact with each other during copper plating treatment.

It is desired that the copper plating apparatus 2 for a gravure cylinder of the present invention further include a copper plating solution automatic management mechanism as described in Patent Document 5, but detailed description thereof is omitted.

The copper plating solution automatic management mechanism adjusts the concentrations of copper and sulfuric acid in the copper plating solution stored in the reservoir bath. In the case where the copper plating solution contains, for example, copper sulfate (CuSO₄.5H₂O) with a concentration of 200 to 250 g/L, sulfuric acid (H₂SO₄) with a concentration of 50 to 70 g/L, chlorine (Cl) with a concentration of 50 to 200 ppm, and additives with a concentration of 1 to 10 mL/L such as a brightener and a burn prevention agent, as copper plating with respect to the gravure cylinder proceeds, the concentration of copper ions in the copper plating solution decreases, and free sulfuric acid increases. Thus, the copper plating solution automatic management mechanism is introduced for the purpose of adding cupric oxide (CuO) to effect a reaction: CuO+H₂SO₄→CuSO₄+H₂O to adjust the reduced concentration of copper ions. This is preferred because it is not necessary to perform the conventional periodic maintenance of the copper plating solution and the disposal of a waste liquid.

EXAMPLES

The present invention is described more specifically by way of examples below. It should be noted that these examples are shown for illustrative purposes and should not be interpreted in a limited manner.

In the following Examples 1 to 3, the following common configuration was used. As a plating apparatus, the plating apparatus having the configuration illustrated in FIG. 3 was used. As a copper plating solution, a copper sulfate plating solution was used, which had a copper sulfate concentration of 220 g/L, a sulfuric acid concentration of 60 g/L, and a chlorine concentration of 120 ppm, and contained, as additives, 5 mL/L of “Cosmo RS-MU” (produced and sold by Daiwa Special Chemical Co., Ltd.) and 2 mL/L of “Cosmo RS-1” (produced and sold by Daiwa Special Chemical Co., Ltd.). As powder supplied by the copper plating solution automatic management mechanism, cupric oxide powder “Fusible copper oxide (ES-CuO)” (produced and sold by Tsurumi Soda Co., Ltd.) was used. As an insoluble electrode, an electrode obtained by coating the surface of a titanium plate with iridium oxide was used.

Example 1

As a gravure cylinder, a cylindrical base of an aluminum core having a circumference of 500 mm and a full length of 1,100 mm was used. The gravure cylinder was mounted in a plating bath under the condition that both ends of the gravure cylinder were chucked by the chuck means including the thermal cooling means as illustrated in FIG. 1. Insoluble electrodes were brought close to gravure cylinder side surfaces up to an interval of 30 mm with a slide mechanism controlled by a computer, and the copper plating solution was overflowed so that the gravure cylinder was soaked completely. The rotation speed of the gravure cylinder was set to 120 rpm, a liquid temperature was set to 40° C., and a current density was set to 16 A/dm² (total current of 890 A and voltage of 7 V). As illustrated in FIGS. 8 and 2, electrodes including lower end portions curved inward were used. Copper plating was performed to a thickness of 100 μm under this condition. The time required for plating treatment was about 20 minutes. The end surface shape of the cylinder subjected to the plating treatment was measured by a laser measurement device. There were no rashes and pits on a plating surface, and plating with a uniform thickness was performed over the full length of the gravure cylinder. In particular, the uniformity of the thickness of plating was kept also in both ends of the gravure cylinder, and thus, the vicinity of both ends of the gravure cylinder was prevented greatly from being plated thicker than the body portion.

Example 2

The same result as that of Example 1 was obtained, when plating treatment was performed in the same way as in Example 1 except for using a cylindrical base of an aluminum core having a circumference of 430 mm and a full length of 1,100 mm as a gravure cylinder.

Example 3

The same result as that of Example 1 was obtained, when plating treatment was performed in the same way as in Example 1 except for using a cylindrical base of an aluminum core having a circumference of 920 mm and a full length of 1,100 mm as a gravure cylinder.

In the above-mentioned embodiment of the present invention, an example is described in which copper plating is performed with respect to a gravure cylinder. However, the present invention is not limited to this example. The present invention can also be applied to the case where chromium plating is performed with respect to a gravure cylinder and to the case where plating other than copper plating is performed with respect to other cylindrical objects to be plated. For example, the present invention can be similarly applied to the case where nickel plating is performed with respect to a printing cylinder for rotary screen printing.

Further, in the above-mentioned embodiment of the present invention, the structure illustrated in FIG. 1 is described as the thermal cooling means 100. However, for example, known thermal cooling means such as heat pipe means can also be applied.

REFERENCE SIGNS LIST

2: copper plating apparatus for gravure cylinder, 4: base, 6: bearing, 8: cover plate, 10: plating bath, 11: discharge duct, 12: collecting port, 14: chuck means, 14 a: tip of chuck means, cylinder holding section, 14 b: trailing end of chuck means, 16: spindle, 18: sprocket, 20: busbar, 21: auxiliary member, 22: insoluble electrode, 23: support bar, 30: geared motor, 31: mounting angle bar, 32, 33, 34, 35, 38: spur gear, 39: fixture, 40: fixture, 43, 44, 45, 46, 47, 48: sprocket, 50, 52: linear rail, 54, 55: guide member, 58, 59: mounting frame, 60, 62: rack, 70: reservoir bath, 80: filter, 86: heater, 88: heat exchanger, 100: thermal cooling means, 102: main pipe portion, 104: cooling medium, 106 cooling medium flow path, 108: inflow port, 110: outflow port, 112: external flow path, 114: circulation pump means, 116: cooling device, 300: gravure cylinder, 302: rectifier, 304: copper plating solution, 306: cylinder rotation motor, C, C1, C2, C3: chain, P: circulation pump, P1: pump. 

1. A plating apparatus for a cylinder, comprising: a plating bath to be filled with a plating solution; chuck means for holding a long cylinder at both ends in a longitudinal direction so as to be rotated and energized, and accommodating the long cylinder in the plating bath; and a pair of opposed insoluble electrodes which is vertically installed so as to face both side surfaces of the long cylinder in the plating bath, and is supplied with a predetermined current, the pair of opposed insoluble electrodes being brought close to both the side surfaces of the long cylinder with a predetermined interval to perform plating on an outer peripheral surface of the long cylinder, wherein the chuck means comprises thermal cooling means, and the thermal cooling means comprises a cooling medium and causes the cooling medium to circulate to cool a cylinder holding section of the chuck means so that heat accumulation in the long cylinder, in particular, a cylinder end portion and the cylinder holding section of the chuck means is eliminated.
 2. A plating apparatus for a cylinder according to claim 1, wherein the thermal cooling means comprises: a main pipe portion provided adjacent to the cylinder holding section of the chuck means; a cooling medium flow path formed in the main pipe portion, for distributing the cooling medium; an external flow path provided in communication with an inflow port and an outflow port of the cooling medium flow path; a cooling medium sealed in the cooling medium flow path and the external flow path; circulation pump means which is installed in the external flow path and functions so that the cooling medium sealed in the cooling medium flow path and the external flow path flows into the cooling medium flow path from the external flow path through the inflow port and flows out to the external flow path from the cooling medium flow path through the outflow port; and a cooling device which is installed in the external flow path and functions to cool the cooling medium flowing out of the outflow port.
 3. A plating apparatus for a cylinder according to claim 1, wherein the plating solution is a copper plating solution or a chromium plating solution, and the long cylinder is a hollow cylindrical gravure cylinder.
 4. A plating apparatus for a cylinder according to claim 2, wherein the plating solution is a copper plating solution or a chromium plating solution, and the long cylinder is a hollow cylindrical gravure cylinder. 